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  • Wiley-Blackwell  (29)
  • Nature Publishing Group  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A gas-phase reactor system was developed to polymerize ethylene using the MgCl2/ethyl benzoate (EB)/TiCl4+ triethylaluminum (TEA) catalyst. The reproducibility of the reactor was tested and found to be adequate for kinetic study. The effects of TEA and temperature were studied with the multisite model that assumes a multiplicity of active sites. It was found that the productivity increased with Al/Ti molar ratio while initial activity leveled off. The deactivation rate, after an initial increase, Al/Ti molar that assumes a multiplicity of active sites. It was found that the productivity increase, decreased with Al/Ti. This corresponded with a transition in deactivation order: below Al/Ti = 70, first-order deactivation was predominant; above Al/Ti = 70, second-order deactivation was predominant. The second-order deactivation reactions were made less disperse at higher Al/Ti. Molecular weight of the polyethylene was very high (〉 1,000,000) indicating negligible transfer reactions. For Al/Ti 〉 130 a monomer sorption limitation for polymerization was found. The effect of temperature was also studied with a maximum in productivity at 55°C for Al/Ti = 98.0 and no maximum when Al/Ti = 53.0. Apparent activation energies (Ea) for activity were found to be 19.5 ±3.3 kJ/mol at Al/Ti = 98.0 and 9.3±1.1 kJ/mol at Al/Ti = 53.0. for deactivation Ea was found to be 36.6±5.0 kJ/mol at Al/Ti = 98.0 and-15.5± 4.4 kJ/ mol at Al/Ti = 53.0. Temperature increased the dispersity of second-order deactivation reactions. © 1993 John Wiley & Sons, Inc.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Deformation of polycarbonate (PC) impact-modified with a core-shell rubber (MBS) was examined at the microscale and nanoscale. The stress-whitened zone (SWZ) that formed ahead of a semicircular notch was sectioned and examined in an optical microscope and transmission electron microscope. At the microscale, the texture of the SWZ consisted of fine shear lines that formed when cavitation of the rubber particles relieved triaxiality and enabled the PC matrix in the SWZ to deform in shear. Examination of thin sections from the SWZ in the transmission electron microscope revealed nanoscale deformation of the rubber particles. When the particle concentration was low (2%), only random cavitation of rubber particles was observed. At higher particle concentrations (5 and 10%), cooperative cavitation produced linear arrays of cavitated particles. The matrix ligaments between cavitated particles were strong enough that they did not fracture; higher strains were accommodated by particle cavitation and matrix extension in the regions separating the arrays. The cavitated arrays were also observed in the damage zone that accompanied the fracture surface of specimens impacted at -20°C. Cooperative cavitation may have implications for the impact strength of blends with higher concentrations of rubber particles. The possibility that particle-particle interactions facilitate cavitation and promote matrix shear deformation is especially relevant to low-temperature impact strength. © 1995 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 1229-1235 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Slurry polymerization of propene using MgCl2-supported TiCl4/dioctylphthalate catalysts were carried out in a semibatch reactor at a constant pressure to examine the effects of polymerization conditions on catalyst activity and polymer isotacticity. The catalysts were prepared at 80, 90, and 105°C, which gave different compositions of chemical complexes associated with the diester. Five alkyl aluminums (triethyl, triisobutyl, tri-n-hexyl, tri-n-octyl, and isoprenyl) were studied as cocatalysts. Among these, triethyl aluminum was found to be most effective for the catalysts prepared at 80 and 95°C, and tri-n-hexyl aluminum for the catalyst prepared at 105°C. Dimethoxydiphenyl silane and 2,2,6,6-tetramethylpiperidine were employed to study their effects as an external Lewis base for the catalyst prepared at 105°C. In both cases, a small amount of either base resulted in significant increase in activity and isotacticity, which can be attributed to the high level of phthaloyl chloride complex in the catalyst. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0570-0833
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0173-2803
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The unexpected crystallinity of free radically polymerized poly(p-vinyltrifluoroacetophenone) (PVTFA) due to lateral order was previously found in this laboratory. To further the understanding of the relationship between chemical structure and crystalline order in polymers of the PVTFA type, polymers of similar structure were synthesized and characterized by differential scanning calorimetry (DSC). These polymers were poly(p-vinyldifluoroacetophenone) (PVDFA), poly(p-vinylphenylheptafluoropropyl ketone) (PVHFK), poly(p-vinylacetophenone) (PVA), and poly(p-vinylphenyltrifluoromethyl carbinol) (PVPTC). Only PVTFA had a crystalline melting temperature (188°C); 220-MHz nuclear magnetic resonance (NMR) measurements on the microstructure of PVTFA and PVDFA revealed broad peaks for the chain protons. The PVTFA was therefore assumed to be predominantly atactic. The results suggested that the unusual crystallinity of PVTFA was related to the unique size and interaction of the trifluoroacetyl moiety on the polymeric side chain.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Prior to the study of poly(o- and p-vinylbenzyl trifluoromethyl ketone) (PVTFK) polymers and their reaction with alcohols, the reactions of some simple model compounds with alcohols were investigated. The reaction of fluorinated ketones toward alcohols was determined by proton nuclear magnetic resonance (NMR) spectroscopy. Two fluorinated ketones-p-methylbenzyl trifluoromethyl ketone (p-MTFK) and o-methylbenzyl trifluoromethyl ketone (o-MTFK)-were prepared. Studies of the reaction of p-MTFK and o-MTFK to various alcohols based on NMR produced equilibrium constants (1M in CCl4) at 31°C that ranged from 0.1 to 6.0. The equilibrium constants for p-MTFK with alcohols were larger than those for o-MTFK. In addition, the equilibrium constants for primary alcohols were larger than those for secondary and tertiary alcohols. Steric effects in this reaction could explain the lowered equilibrium constants for o-MTFK and the secondary and tertiary alcohols.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Copolymers of styrene/p-vinyltrifluoroacetophenone were prepared by two different reaction routes: (1) modification of polystyrene with trifluoroacetyl chloride and (2) copolymerization of styrene and p-vinyltrifluoroacetophenone (VTFA). There appears to be a limit to the modification method because only a maximum content of 14.5 mole % trifluoroacetyl functionality could be attached to the polymer before the onset of crosslinking. Differential scanning calorimetry (DSC) was used to determine their Tg's. In addition, the reactivity ratios of styrene and VTFA were investigated. The reactivity ratios and Q and e values were r1 = 0.30 ± 0.09 (styrene) and r2 = 1.3 ± 0.3 (VTFA); Q1 = 1.0 and e1 = -0.8 (styrene); Q2 = 0.44 and e2 = 1.93 (VTFA).
    Additional Material: 4 Ill.
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  • 10
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of new fluorinated ketone-containing polymers, poly(p-vinyltrifluoroacetophenone) (PVTFA), poly(p-vinyldifluoroacetophenone) (PVDFA), poly(p-vinylphenylheptafluoropropyl ketone) (PVHFK), and poly(o-and p-vinylbenzyltrifluoromethyl ketone) (PVTFK), were prepared by the free radical polymerization of the corresponding monomers. The monomers, p-vinyltrifluoroacetophenone (VTFA), p-vinyldifluoroacetophenone (VDFA), p-vinylphenylheptafluoropropyl ketone (VHFK), and o-and p-vinylbenzyltrifluoromethyl ketone (VTFK), were prepared by the reaction of Grignard reagent with the corresponding perfluoroacid or its lithium salt. Polymerization was a competitive side reaction during monomer preparation. Reduced side reaction and higher yields of monomer (based on the Grignard reagent) were obtained from the lithium salt of the perfluoroacid, compared with the perfluoroacid itself. These new substituted polystyrenes which contain fluorinated ketone functionality were characterized by their ability to (1) react with active hydrogen compounds such as alcohols or water; (2) have high glass transition temperatures and decreased solubility in nonpolar solvents (e. g., benzene) compared with polystyrene; and (3) be converted into other functional groups such as alcohols or acids by treatment with the appropriate chemical reagents. Beads of a styrene (ST) terpolymer with 2% divinylbenzene (DVB), which contained the CF3COCH2 function, were prepared by suspension polymerization of ST, VTFK, and DVB. The terpolymer, which contains 15-17% mole (or 0.70-0.71 meg/g) of CF3COCH2 swollen with a solvent, were shown to chemisorb alcohols.
    Additional Material: 4 Ill.
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